It is well known that pultrusion processes are effective continuous processes for producing articles of constant cross-section. Conventional pultrusion processes involve drawing a bundle of reinforcing material (e.g., glass filaments or fibers) from a source thereof, wetting the fibers and impregnating them (preferably with a thermosettable polymer resin) by passing the reinforcing material through a resin bath in an open tank, pulling the resin-wetted and impregnated bundle through a shaping die to align the fiber bundle and to manipulate it into the proper cross-sectional configuration, and curing the resin in a mold while maintaining tension on the filaments. Because the fibers progress completely through the pultrusion process without being cut or chopped, the resulting products generally have exceptionally high tensile strength in the longitudinal (i.e., in the direction the filaments are pulled) direction. Exemplary pultrusion techniques are described in U.S. Pat. Nos. 3,793,108 to Goldsworthy; 4,394,338 to Fuway; 4,445,957 to Harvey; and 5,174,844 to Tong. Exemplary pultruded articles include tool handles, mine shaft bolts, pipes, tubing, channel, beams, fishing rods and the like.
Of particular interest is the manufacture of fiber reinforced rods or bars ("rebar"). Such bars are often used in cementitious mixtures, such as concrete, as reinforcing members. Concrete typically has a high compressive strength, but is relatively weak in tension, so the inclusion of high-tensile strength rebar beams enhances the tensile strength, and thus the overall performance, of the concrete considerably. Fiber-reinforced rebar has drawn attention because some compositions are corrosion-resistant and thus potentially offer a solution to the corrosion problem that has plagued steel rebar in concrete. An exemplary corrosion-resistant fiber-reinforced rebar, disclosed in co-pending U.S. patent application Ser. No. 08/467,157, comprises a fiber reinforced thermoset core and an outer cladding formed of sheet molding compound (SMC).
Because different cement and concrete compositions and structures can have different performance and cost parameters, it is desirable to provide different compositions of fiber-reinforced rebar to meet these different demands. With different rebar compositions come different equipment concerns, particularly for continuous manufacture of such compositions.
In view of the foregoing, it is an object of the invention to provide an apparatus combining a pultrusion apparatus and an apparatus for molding an outer cladding on rebar.
It is another object of the invention to provide an apparatus for making reinforcing structural rebar comprising a pultruded core of a thermosetting resin and an outer cladding thereon.
Other objects, features, and advantages of the invention will be particularly identified below.